Hooks: Update deny_binary to correctly handle pushes to new repos

Before, the hook would allow pushing binary files to newly created empty
repos. Now we handle and test this in our test suite.

hooks/deny_binary

@@ -28,9 +28,17 @@ while read oldrev newrev refname; do
     continue
   fi
 
-  # Set oldrev to HEAD if this is branch creation.
   if [ "$oldrev" = "$nullsha" ]; then
-    oldrev="HEAD"
+    if [ $(git rev-parse HEAD) = "HEAD" ]; then
+      # Iterate over all commits if there is no HEAD.
+      # This happens when the repo has just been initalized
+      rev_range=${newrev}
+    else
+      # Don't iterate over any commits already in the default branch of the repo
+      rev_range=HEAD..${newrev}
+    fi
+  else
+    rev_range=${oldrev}..${newrev}
   fi
 
   # Check for branches and tags, but not pull requests in refs/pull. Otherwise Gitea
@@ -44,7 +52,7 @@ while read oldrev newrev refname; do
   fi
 
   # Loop over each commit.
-  for commit in $(git rev-list --objects ${oldrev}..${newrev} |
+  for commit in $(git rev-list --objects ${rev_range} |
     git cat-file --batch-check='%(objectname) %(objecttype) %(objectsize) %(rest)' | grep commit | awk '{print $1}'); do
 
     # Get list of potentially binary files in this commit